Carbon disulfide process



crc. 7, 1947. c. M. THAcKl-:R 2,428,727

CARBON DISULFIDE PROCESS Filed D60. 26, 1942 :hv- 0S anale, litiga .'57/53 Stripper and Sulphur i-S Spaz'atoz' /55 I l l @was )Zaacor \j9 Z9Heater Sulphur t fS\ Condenser j \j'5 .9 CSZJJQSSJL ldz aai'alyc. lChambel" l mvENToR Carlisle M Thacker BY @Pvtzez' (Deland vq, HarneyPatented Oct. 7, 1947 CARBON DISULFIDE PROCESS Carlisle M. Thacker,Highland Park, Ill., assignor to The Pure Oil poration of Ohio Company,Chicago, Ill., a cor- Application December 26, 1942, Serial No. 470,303

2 Claims.

This invention relates to a preparation of carbon disulfide fromhydrocarbons and is more particularly concerned with a continuousprocess involving recovery of sulfur from the efiuent products of theprocess and recycling of the recovered sulfur to the process.

In my application, Serial No. 294,319, led September 11, 2,330,934,issued October 5, 1943, Vthere is disclosed and claimed a process forpreparing carbon disulfide from hydrocarbons, such as methane, byreacting the hydrocarbons with sulfur at temperatures of 450-750 C. inthe presence of a catalyst selected from the group consisting of silicagel, fullers earth, bauxite, activated alumina, and in general thosetypes of clay which have been found effective in the removal of colorproducing and gum forming constituents in petroleum oils. Thesecatalysts may be used alone or together with one or more metal compoundsof metals of groups V, VI, VII and VIII of the periodic table. Oxides orsuldes of the aforementioned metals are useful as catalyst promoters. Asexamples of metal compounds which may be used as promoters inconjunction with the silica gel, fullers earth, activated alumina orbauxite or the oxides or sulfides of iron, vanadium, chromium,molybdenum and manganese. Space velocities of 400 to 10,000 volumes ofgas per hour or even higher space velocities may be used. By spacevelocity is meant the ratio of total volume of gases at C. and 760 mm.pressure passed over the catalyst per hour to the volume of the spaceoccupied by the catalyst. Under the conditions outlined, over 90% byweight of the methane or other hydrocarbons charged can be convertedinto carbon disulfide in one passage through the catalyst bed.

The reaction proceeds in accordance with the following equation:

In order to make this process competitive with present commercialprocesses for making carbon disulfide, it is either necessary to recoversulfur from the hydrogen sulfide formed or to have a profitable means ofdisposal or use for the hydrogen sulfide.

An object of the invention is to prepare carbon disulfide fromhydrocarbons and sulfur.

Another object of the invention is to provide a method for recoveringcarbon disulfide and sulfur from gases and vapors containing substantialamounts of carbon disulfide and hydrogen sulfide.

1939, now U. S. Patent No.

A further object of the invention is to provide an economical processfor converting hydrocarbons into carbon disulde at relatively lowtemperatures.

Other objects and advantages of the invention will become apparent fromthe following description and accompanying drawing of which the singlefigure is a schematic flow diagram showing the various steps in theprocess.

In accordance with my invention the gases leaving the carbon disulfidereaction chamber are cooled sufficiently to condense unreacted sulfur,which is separated from the remaining vapors and recycled to thecatalytic chamber. The remaining products of the reaction consistingprimarily of carbon disulfide, hydrogen sulfide, unreacted hydrocarbons,and a small amount of hydrogen are passed to a reactor wherein they arecontacted with an aqueous solution of sulfur dioxide. The hydrogen suldeand sulfur dioxide react in the presence of water to form sulfur andwater in accordance with the following sulfide does not appreciablyreact and therefore is readily separated from the aqueous phase of thereaction mixture, together with hydrocarbons and hydrogen and can bereadily fractionated from the mixture to form a substantially pureproduct.

In order to better understand my invention reference should be made toaccompanying drawing. The drawing should be read with the longer rightside thereof considered as the bottom. Numeral I indicates a linethrough which sulfur is charged to the catalytic reaction chamber 3. Thesulfur may either be in molten or vapor form, depending on thetemperature and pressure maintained in the catalyst chamber. Although Iprefer to operate at atmospheric pressure, super-atmospheric pressuresmay be used. As catalyst, I prefer to use an activated form of bauxite,although I may use any of the catalysts previously disclosed, as well assuldes of the metals .of the 8th group of the periodic system,preferably supported on a catalyst carrier such as diatomaceous earth,pumice or bauxite with or without a promoter, such as thorium oxide,chromium oxide or cerium oxide. Methane or other hydrocarbons, such asethane, propane, butane, ethylene, propylene or butylene, as Well asmixtures thereof, or even higher boiling hydrocarbons, may be charged tothe catalytic chamber through lines 5 and 7. Both the hydrocarbon andthe sulfur are preferably heated to approxithem to the catalyticchamber.

The temperature of the catalyst is maintained within the range of45o-750 C., and preferably within the range of 45o-700 C., althoughhigher temperatures may be used. The process is applicable to anyprocess for preparing carbon dii sulfide from sulfur andhydrocarbonswherein a substantial amount of hydrogen sulfide is formedas one of the reaction products.

In the catalytic chamber 3 the sulfur and hydrocarbon react to formprimarily carbon disulfide and hydrogen sulfide together with somehydrogen. When operating with a stoichiometric ratio of sulfur tomethane or a slightly higher sulfur-methane ratio, the amount ofhydrogen` formed will depend chiefly on the temperature of reaction, itbeing very small within the preferred temperature range and increasingas the temperature increases above the preferred range.

The reaction products, including unreacted suifur and hydrocarbon, leavethe catalyst chamber through line 9 and pass to sulfur condenser IIwherein the temperature is lowered to a temperature well below theboiling point of sulfur but not below the boiling point of carbondisulfide. The temperature in the sulfur condenser will preferably beabout 12C-130 C. The temperature within the sulfur condenser shouldpreferably be adjusted to keep the sulfur in mobile liquid phase so thatit may be easily recycled through lines I3 and I5 to the catalyticchamber 3. The carbon disulfide, hydrogen sulfide, unreactedhydrocarbons, and hydrogen leave the sulfur condenser as a gas-vapormixture through line I1 and pass to a hydrogen sulde-sulfur dioxidereactor I9, in which the vapors contact an aqueous solution of sulfurdioxide. An aqueous sulfur dioxide solution or a mixture of a saturatedaqueous sulfur dioxide solution and sulfur dioxide gas may be fed to thereactor through line 2|. The contact between the reaction vapors and theaqueous sulfur dioxide is preferably countercurrent. In the hydrogensuliide-sulfur dioxide reactor, hydrogen sulfide reacts with the sulfurdioxide to form sulfur and water. If the temperature of the hydrogensulfide-sulfur dioxide reactor is maintained below the melting point ofsulfur, the suifur will precipitate in the water as a colloid. If,however, the system is carried under super atmospheric pressure,sufficiently high to keep the water in the liquid phase at the meltingpoint of sulfur, the sulfur will agglomerate and form a liquid body atthe bottom of the reactor. The reactor I9 may be maintained at atemperature from atmospheric to approximately 130 C. The process can becarried out by feeding to reactor I9 a stoichiometric ratio of sulfurdioxide to hydrogen sulfide or by feeding sulfur dioxide in an amountlower than or in excess of the stoichiometric ratio. Itis preferred,however, to maintain the sulfur dioxide-hydrogen sulfide ratio at orvery near the stoichiometric ratio required for production of sulfur andwater.

A satisfactory method of separation is to feed an excess of sulfurdioxide and to maintain reactor I9 at substantially atmospheric pressureand at a temperature below 100 C. so that the water will remain inliquid phase and hold the sulfur in colloidal suspension. The water,containing the suspended sulfur, is withdrawn from the bottom of thereactor through line 25 and pump 21 wherein the pressure is raised to atleast 25 pounds per square inch gauge.' The water suspension of sulfuris then heated in heater 29 temperature and pressure conditionsoutlined, the t sulfur melts and agglomerates into a liquid whichseparates in the bottom of tower 3,3 from which it is recycled throughlines 35 and I5 to the catalytic chamber 3. Under these conditions oftemperature and pressure. the water can be withdrawn as liquid from anintermediate portion of the stripper through line 31. This water may berecycled to an absorber (not shown) for preparing aqueous sulfur dioxidefor charging to reactor I9.

The aqueous phase withdrawn from reactor I9 may contain a small amountof carbon disuliide and sulfur dioxide which are vaporized in stripper33.

The carbon disulfldevapors together with a small amount of water vaporand sulfur dioxide pass from the top of the stripper through line 39 andjoin the hydrogen-carbon disulfide-hydrocarbon vapor leaving the top ofreactor I9 through line 4I. The combined vapors pass through line 43 andcooler 45 into separator 41. In the cooler 45 the temperature is reducedsufilciently to condense carbon disulfide, which is withdrawn from thebottom thereof as liquid through line 49. This crude carbon disulfidecan be purified by distillation. Any sulfur dioxide recovered in thisdistillation can be recycled to reactor I9 through line 2| or can beabsorbed in water from stripper 31 and/or separator 41 prior toreturning it to the reactor. Any water contained in the vapors islikewise condensed and may be withdrawn from an intermediate portion ofthe separator 41 through line 5I. This water will contain therein aportion of sulfur dioxide contained in the vapors, and may be recycledthrough line 52 to the upper portion of the reactor I9. All or a portionof this water may be withdrawn through line 53 and used in preparationof aqueous sulfur dioxide solution for charging to reactor I9 throughline 2|. The remaining gases consisting chiefly of unreactedhydrocarbons and possibly hydrogen is withdrawn from the separatorthrough line 54 and recycled through lines 55 and 1 to the catalyticchamber 3, or withdrawn from the system through line 51. If desired, aportion of the gas may be recycled and a portion eliminated from thesystem. The disposal of the gas leaving line 51 will depend somewhatupon the available gas supply and the amount of sulfur compoundscontained therein. Where the supply of methane or other hydrocarbon isample and constitutes a waste product and where the sulfur content ofthe gas is suiliciently low it may be desirable to eliminate the 'gasesleaving separator 4,1 through line 51 from to recover hydrogen sulfidefrom these products and to convert other sulfur compounds such asmercaptans, which may lbe contained in the carbon disuliide to carbondisulfide.

Iclaim:

1. The process of preparing carbon disulilde comprising contactinghydrocarbons and sulfur in a conversion zone under conditions such as tosulfur, the amount of sulfur yield carbon disulfide and hydrogen sulfideas the products comprising chiefly carbon disuliide and' -hydrogensuliide with water and sulfur dioxide at a temperature below 100 C. inorder to form dioxide being approximately the stoichiometric equivalento1' the hydrogen sulfide and the water being less than the amountrequired to give a saturated solution of sulfur dioxide, separatingsuspended sulfur from the aqueous medium and recycling the sulfur to theconversion zone, separating carbon disulde from the aqueous medium andfrom the remaining reaction products and collecting the same, recoveringexcess sulfur dioxide from the reaction gases in a portion oi theaqueous medium from which sulfur has been separated and recyclingaqueous medium containing dissolved sulfur dioxide to the sulfur formingstep. 2. Process in accordance with claim 1 in which the aqueous mediumcontaining Suspended sulfur is heated under pressure to a temperaturesumcient to melt sulfur but below the boiling point oi' water and thesulfur is recycled to the conversion zone in molten state.

CARLISLE M. THACKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Mellor, Comprehensive Treatise onInorganic and Theoretical Chemistry," vol. 10, 1930, page 134, Longmans,Green 8: Co., London, England.

